Bismutite

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Bismutite
Bismutit (Wismutcarbonat) - Schneeberg, Erzgebirge.jpg
Bismutite from Schneeberg, Germany
General
CategoryCarbonate mineral
Formula
(repeating unit)
Bi2(CO3)O2
Strunz classification5.BE.25
Dana classification16a.03.05.01
Crystal systemOrthorhombic
Crystal classPyramidal (mm2)
(same H-M symbol)
Space groupImmm
Unit cella = 3.865 Å, b = 3.862 Å,
c = 13.675 Å; Z = 2
Identification
ColorYellow to brown, greenish, green-grey, grey or black
Crystal habitVery rare as platy crystals; typically radially fibrous to spheroidal, in crusts and earthy to dense massive aggregates
Twinningpseudo-merohedral twinning simulates tetragonal symmetry
CleavageDistinct/Good on {001} (microscopically observable)
Mohs scale hardness2.5 - 3.5
LusterVitreous, waxy, may be dull to earthy
StreakGrey
DiaphaneityOpaque to transparent in small grains
Specific gravity6.7 - 7.4 measured, 8.15 calculated
Optical propertiesBiaxial (-) (appears uniaxial due to twinning)
Refractive indexa=2.12-2.15, b=2.12-2.15, g=2.28
Birefringence0.1300-0.1600
2V angle45
References[1][2][3][4]

Bismutite or bismuthite is a bismuth carbonate mineral with formula Bi2(CO3)O2 (bismuth subcarbonate). Bismutite occurs as an oxidation product of other bismuth minerals such as bismuthinite and native bismuth in hydrothermal veins and pegmatites,[2] it crystallizes in the orthorhombic system and typically occurs as earthy to fibrous masses.[1]

It was first described in 1841 for an occurrence in Saxony.[1]

The term bismuthite has been used in the past for bismuthinite.[5]

References[edit]

  1. ^ a b c Webmineral
  2. ^ a b Mindat
  3. ^ Handbook of mineralogy
  4. ^ Grice, Joel D., A Solution to the Crystal Structures of Bismutite and Beyerite, The Canadian Mineralogist, Vol. 40, pp. 693-698 (2002)
  5. ^ Chisholm, Hugh, ed. (1911). "Bismuthite" . Encyclopædia Britannica. 4 (11th ed.). Cambridge University Press. p. 11.